SUMMARY OF PROPOSED WORK: This proposal contains plans for the study of the organization of immunoglobulin genes and of the control of immunoglobulin synthesis in B and T cells. The first project is directed at the question whether genes for the constant region and the specific variable region of an immunoglobulin are translocated next to each other for contiguous transcription in a cell which produces an immunoglobulin with that particular variable region. These experiments will further investigate the concept of allelic exclusion and are hoped to lead eventually to a resolution of the problem of the generation of antibody diversity. The other project is an extension on our finding that T lymphocytes contain mRNA for kappa-chains. We will be investigating whether mRNAs for H-chains are present in T cells by molecular hybridization with complementary DNA for M, G, and A H-chains, and by cell free translation of T cell RNA combined with specific immuno-precipitation.